Work pieces, for instance items which are to be annealed, hardened, sintered, etc., are heated to extremely high temperatures in a vacuum furnace. A vacuum furnace is used to heat such items for a number of reasons. For instance, if such items were heated in the atmosphere, the items would become oxidized and that would be unacceptable. However, after the items have been "heat treated" in a vacuum furnace, there is a need to cool such items so that when they are removed from the vacuum furnace, they will no longer be at high temperatures and, therefore, will no longer oxidize in the course of being so removed. In some instances a rapid quenching, or cooling, is desirous to effect certain characteristics in the workpiece. For instance in heat treating certain grades of stainless steel and in the hardening of tool steels, rapid quenching is desirous.
Accordingly vacuum furnaces have, in the prior art, provided arrangements for quenching or cooling the workpiece. A popular technique and the necessary hardware to effect that technique is described in connection with a discussion of FIG. 1 and consists of a network of pipes connected to a manifold means. Inert gas is pumped into the manifold means under pressure when quenching is to take place. The inert gas flows from the manifold means, through the various pipes into the hot zone chamber of the vacuum furnace. While this arrangement has been satisfactory and is in great use, it does have some serious infirmities. The infirmities lie in two major areas although, indeed, there are lesser infirmities as well. When the system needs to be repaired, for instance because one or more of the heating elements in the hot zone chamber, wears (due to thermal expansion and contraction) and breaks, the entire pipe assembly must be removed in order to be able to get the hot zone assembly out of the vacuum furnace chamber. During such maintenance efforts in the prior art, the pipes, which are brittle, break. In addition, in the prior art arrangement, the inert gas flows into the hot zone chamber in a non-uniform way and such non-uniformity requires the need of excess amounts of inert gas to be certain that all of the workpiece is cooled properly. In my U.S. Pat. No. 4,395,832, entitled "A Gas Duct Arrangement For A Vacuum Furnace," I teach a plenum which overcomes the problems related to pipes breaking during maintenance, and which provides substantially uniform inert gas flow into the hot zone chamber and, therefore, to the workpiece for cooling. While the structure that I teach in my above mentioned patent, does provide an improved means for introducing inert gas into the hot zone chamber, no structure is without some room for improvement. In field use of my structure, described in U.S. Pat. No. 4,395,832, I have found that the uniformity of gas flow into the hot zone chamber of the vacuum furnace is decidedly improved over the prior art, but I have also found that if I add baffles as described in this patent application, the uniformity of the gas flow is increased even more.